1. Field of the Invention
The present invention relates to a digital signal receiver, and more particularly, to a digital signal receiver to which a self-recovering equalization algorithm is applied for an initial predetermined time and a decision directed algorithm is applied after the predetermined time has lapsed and a method for receiving a digital signal.
2. Description of the Related Art
FIG. 1 shows the structure of a conventional digital signal receiver, which is a part of European Patent Application No. 92112305.5 (Publication No. 524559) entitled “Carrier Phase Recovery for an Adaptive Equalizer”.
The digital signal receiver shown in FIG. 1 includes a transmitter 10, a channel 120, a carrier recovery loop circuit 100, and a decoder 60. The carrier recovery loop circuit 100 includes a demodulator 30, an adaptive equalizer 40, and a carrier recovery unit 50.
A received signal at the transmitter 10 is input to the demodulator 30 through the channel 120. The adaptive equalizer 40 receives the signal demodulated by the demodulator 30 and compensates for the distortion of the signal generated by the channel 120. The output signal from the adaptive equalizer 40 is input to the carrier recovery unit 50, thus generating a control signal according to frequency offset and controlling the demodulation frequency of the demodulator 30.
The carrier recovery unit 50 is required to compensate for the frequency offset generated by the inconsistency of oscillators used for a digital signal transmitter and a digital signal receiver. A phase lock detector in the carrier recovery unit 50 detects the frequency offset of the carrier recovery unit 50 and converts the algorithm of the adaptive equalizer 40 from a first algorithm to a second algorithm, thus reducing remaining errors.
However, in a conventional technology, since the adaptive equalizer 40 which is a delay line exists in the carrier recovery loop circuit 100, it is difficult to quickly capture and trace the frequency offset due to the delay of a signal. Since the carrier recovery unit 50 must operate from an initial equalization step, the signal which is not completely equalized is input to the carrier recovery unit 50, thus delaying the time for capturing the frequency offset.